Reduction of toxic gas emissions requires not only an increase in efficiency of energy-intensive activities, but also a limit on the permissible amount of green house gases (GHG) and toxic gases released by manufacturers. With respect to nitrogen dioxide (NO2), the U.S. National Ambient Air Quality (NAAQS) Standards set the permissible annual amount of such emissions at a maximum of 53 parts per billion (ppb), with short term exposures limits (STEL) at one (1) parts per million (ppm) for 15 minute exposures.